Solid hardwood
Solid hardwood installation, nailed or glued, never floated.
Solid hardwood is one piece of wood through its full thickness, and it is fixed to the subfloor, either nailed down over wood or glued down with a full spread of adhesive. It is the floor that can be sanded and refinished for decades, and it is also the floor that punishes a bad subfloor and a dry house the most. So the job is mostly what happens before the first board.
The figures on this page are the National Wood Flooring Association's installation guidelines, quoted with the source beside them. They are not our numbers. The species, grade and width get chosen at the free in-home estimate, with the samples on your own floor.
How it goes down
Two fixing methods, and the subfloor decides which.
Solid wood is not dimensionally stable enough to float. The guidelines say it plainly: solid wood flooring should never be installed using the floating-floor method unless the manufacturer specifically recommends and warrants it.[1] That leaves two honest options.
Nail down
Over a wood subfloor
- Cleats or staples driven through the tongue into the subfloor
- Boards fastened at set intervals along their length, never just at the ends
- Along the starting wall and the last rows, where the nailer will not fit, boards are face-nailed or set in elastomeric adhesive[1]
- The usual method on the upper floors and main floors of houses around here
Full spread glue down
Where nailing is not an option
- Adhesive trowelled across the whole subfloor, not dabbed
- The adhesive and any moisture control system are chosen together, because they have to be compatible
- Tighter flatness tolerance than nail-down, because a hollow under a glued board stays a hollow
- Not a route to putting solid wood in a basement: see below
Not below grade
The one place solid does not go
- The guidelines state solid wood floors should not be installed below grade unless the manufacturer recommends it[1]
- On a slab, the answer is usually engineered hardwood, which is built for it
- We will say so at the estimate rather than sell you the wrong floor
Included, not extra
Ask what other quotes leave out
- Old floor out, same-day disposal
- Baseboard and casing off, then refitted and painted or stained to match
- Furniture moved, there and back
- Doors cut so they clear the new height
The measurable part
What the guidelines actually require.
Anyone can say a floor was "installed properly". These are the published numbers a solid floor is supposed to meet, so you can check.
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Fastener spacing
For ¾" solid strip flooring under 3" wide, the guidelines specify fasteners at 8" to 10" intervals along the length of each board, 1" to 3" from each end joint, and a minimum of two fasteners per board.[1] Thinner solid strip, over ½" and under ¾", tightens to 6" to 8" intervals.[1] A board held at the ends only is the one that squeaks in eighteen months.
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How flat the subfloor has to be
For nail-down with fasteners 1½" and longer, the subfloor should be flat to within ¼" over 10 feet, or 3/16" over 6 feet. Glue-down and shorter fasteners tighten to 3/16" over 10 feet, or 1/8" over 6 feet.[1] Where a subfloor cannot be brought to that, the guidelines call for replacing it or adding a second layer rather than working over it.[1] That is the subfloor work on the quote.
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Moisture, measured, not waited out
Hardwood is manufactured at 6% to 9% moisture content, with an allowance for pieces up to 12%.[1] During the humid season a wood subfloor should not exceed 13%.[1] The guidelines define acclimation as aligning the flooring with the environment it is going into, not as leaving boxes in a room for a week, and they are explicit that the installer must know the ambient conditions, the moisture content of the flooring and the moisture content of the substrate.[1] The meter comes out before anything comes off the truck.
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The room it has to live in
Solid wood wants 30% to 50% relative humidity and 60 to 80°F.[1] A Burlington house in February often sits under 30%, which is why boards shrink and gaps open. The guidelines note that a supplemental humidity control system is often necessary and should be specified into a wood flooring project.[1] Buy a hygrometer before the floor arrives.
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Room to move
The installation details in the guidelines call for a minimum ¾" expansion space at all vertical obstructions, walls included.[1] The baseboard covers it. Baseboard nailed down through the floor instead of to the wall pins the boards and is the other common cause of a floor that buckles.
Sources
- National Wood Flooring Association, Wood Flooring Installation Guidelines, revised 2025. Nail-down fastener schedules for solid strip flooring, the prohibition on floating solid wood, grade-level suitability, subfloor flatness tolerances, manufactured and subfloor moisture content, acclimation, interior temperature and humidity, and expansion space.
Standards last read
Before you buy new
If you already have solid hardwood, ask about refinishing first.
A solid floor can take several sandings across its life, and a worn finish is not a worn floor. Sanding and refinishing competes with replacement, not with other installers, and it is often the cheaper answer. We will tell you at the estimate which one your floor is actually a candidate for, including when the honest answer is that it has had its last sand.
Related
Read next.
- Why a new floor squeaks, cups or gapsMoisture and the subfloor, with the figures. Neither is the wood's fault.
- Engineered vs solid in a Southern Ontario winterThey fail and last in different ways. The documented differences, in a table.
- Subfloor repair and levellingWhat the flatness tolerance means on an actual job, and how it is met.
- Cleaning and caring for a wood floorVinegar and steam are on the do-not list. What to use instead.
Next step
Pick the species on your own floor, in your own light.
The samples come to the house with the free estimate. You get a firm number before we leave, and nothing is owed either way.
- Phone
- 289-689-4242
- referralflooring@gmail.com
- Warranty
- 1 year on floor repair and installation.
- Area
- Burlington, Hamilton, Waterdown, Dundas, Ancaster, Oakville and the wider Golden Horseshoe.